title: Identification and characterization of in vitro metabolites of 2-[2'-(dimethylamino)ethyl]-1,2-dihydro-3H-dibenz [de,h]isoquinoline-1,3-dione (Azonafide).
abstract: Azonafide (2-[2'-(dimethylamino)ethyl]-1,2-dihydro-3H-dibenz[de, h]isoquinoline-1,3-dione) is the parent of a new series of anthracene-containing antitumor agents. Its structure is based on amonafide but lacks a primary amine and has an anthracene chromophore rather than a naphthalene chromophore. Using a rat liver cytosol incubation and HPLC/MS detection, we have identified four metabolites resulting from in vitro metabolism of azonafide. These alkyl-modified derivatives include a mono- and a di-N'-desmethyl metabolite, an N'-oxide metabolite, and a carboxylic acid metabolite. Purified samples of these metabolites were analyzed for cytotoxic activity using a 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium vital dye (mitochondrial reductase) assay and for inhibition of topoisomerase II (TOPO II) using a cell-free enzymatic system. Each metabolite had decreased cytotoxicity relative to azonafide with the following relative potencies in descending order: the mono-N'-desmethyl metabolite, di-N'-desmethyl metabolite, the N-oxide metabolite, and the carboxylic acid metabolite. Similarly, the N'-desmethyl metabolites retained TOPO II inhibitory activity but with lower potency than azonafide. The N-oxide and carboxylic acid metabolites did not inhibit TOPO II at 0. 05 and 0.5 microg/ml, respectively. Thus, metabolism of azonafide by rat liver cytosol represents a detoxification pathway rather than a bioactivation scheme for this DNA intercalator.
authors.affiliation: Department of Pharmacology/Toxicology, University of Arizona, Tucson, AZ 85724, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Mayr
authors.forename: S M
authors.initials: SM
authors.lastname: Sami
authors.forename: W A
authors.initials: WA
authors.lastname: Remers
authors.forename: R T
authors.initials: RT
authors.lastname: Dorr
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000633:toxicity; D016466:CHO Cells; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D003600:Cytosol / Q000201:enzymology; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D008658:Inactivation, Metabolic / Q000502:physiology*; D007364:Intercalating Agents / Q000378:metabolism / Q000633:toxicity; D007546:Isoquinolines / Q000378:metabolism* / Q000633:toxicity; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D013058:Mass Spectrometry; D015394:Molecular Structure; D053644:Naphthalimides; D051381:Rats; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D004278:DNA, Superhelical; D007364:Intercalating Agents; D007546:Isoquinolines; D053644:Naphthalimides; D013778:Tetrazolium Salts; D013844:Thiazoles; C092761:azonafide; D004250:DNA Topoisomerases, Type II; C022616:thiazolyl blue